Hey, I've got a similar thingie.
Leaving tomorrow to a place ~five hours away to a friend's cottage, returning on tuesday (that's three days only).
Me and my GF are taking the train, as five hours in a small car with four people would be...well, hell.
Sucks, because we'll be riding home in the car - but I find the returningtrips to be alot easier, as you're coming home instead of going to some freaky place. :P
I'm guessing I can have some fun with the hellish trip, instead of fearing only the negative sides of it. Every trip makes us stronger, as we collect more of those "I've done this before" - experiences to look back at in future situations, right?
After all, we've done it before and survived (even had some fun most of the times!), so why wouldn't we survive this one?
You'll be fine - and just go to a private place for a while if you get anxious, every place has one!
Oh, and I hate boats too (among other vehicles you can't really get out of) - had to ride in one for a long time one summer. I was really nervous before and to start with, but calmed down as I talked and laughed with some friends. I think they key's really to just face the fact that you are in that situation and it won't change by you panicking about it. Breathe slowly, ignore the heartbeat, and socialize as much as you can. :D
*stops the random writing now* ^___^